For Pokémon Go players looking to have a complete Kanto Pokédex, who have been playing the game since launch, there are a few creatures which may have eluded your grasp.
Farfetch’d, Kangaskhan, Mr. Mime, and Tauros are all region exclusive Pokémon, only available to players in the correct areas of the world, or who have friends who have travelled to North America, Asia, or Australia are are willing to trade.
Mewtwo was only available via EX Raids, a special kind of invite only raid, where players had to frequently raid and capture specific gyms, be lucky enough to get an invite, and had to be free to be at the right place — and the right time — to then attempt the special raid and capture Mewtwo for themselves.
Both sets of creatures were until now fairly rare, with many daily active players still not having them. I've played every day since launch, and I've only ever had one EX raid, and only had region exclusives thanks to work travel. Now, these creatures are going to be much more accessible to UK players who are missing spots in their collection.
As a wrap up to Niantic's summer of Pokémon Go events, an Ultra Unlock is going to make certain creatures significantly easier to capture for over a month.
From September 20th until October 23rd, Mewtwo will be available to players via standard raids, which do not require a random invite and are not limited to a single two hour window on a single day. Players will have multiple chances per day to go and hunt down one of Gen 1's most famous creatures.
Also during the above dates where Mewtwo is available in standard raids, players will be able to hatch Farfetch’d, Kangaskhan, Mr. Mime, and Tauros from 7KM eggs, which are received from friend gifts and normally only hatch Alolan Pokémon. Beyond this, Gen 1 Pokémon will spawn more frequently during the event.
As far as I'm concerned, this is a great bit of news. For hardcore players, many of us have already had the glory of having these exclusive creatures before our friends did, and had time after the launch of Trading to use those exclusive creatures to get things we need in our collections. Now people who've been annoyed by missing spots in their collections have a chance to catch up and feel the joys of Pokédex completion.